Apentix/AP Chemistry/Unit 5: Kinetics/Question

AP Chemistryeasymcq1 pt

An energy profile shows reactants at 50 kJ/mol and products at 20 kJ/mol. Which statement is correct?

A.dH = -30 kJ/mol, so the reaction is exothermic

B.dH = +30 kJ/mol, so the reaction is endothermic

C.Ea = 30 kJ/mol for this reaction

D.The reaction absorbs 30 kJ/mol

Explanation

Core Concept

The enthalpy change equals product energy minus reactant energy: 20 - 50 = -30 kJ/mol. The negative sign marks an exothermic reaction releasing 30 kJ/mol to the surroundings. Nothing in these two endpoint values specifies the barrier height; locating the peak would be needed for Ea. Profile endpoints fix the thermodynamics, while the peak fixes the kinetics.

Correct Answer

AdH = -30 kJ/mol, so the reaction is exothermic

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